Irregular interference or malfunction of equipment is mainly caused by lighting surge, switching surge and electromagnetic pulse. Usually, the three types of surge interference sources intrude through (1) power circuit, (2) signal circuit (control circuit) and (3) grounding circuit. If handing surge energy and discharge current with insufficient capability or an inadequate approach, equipment is prone to faults or interferences. Accordingly, a multitude of existing electronic equipment, communication equipment, control equipment and power equipment is additionally equipped with a surge suppression device to alleviate faults of equipment or interferences to equipment.
Despite a nature of conventional surge suppression devices capable of absorbing transient overvoltage, in-rush current and high energy, surge voltage can usually go up to hundreds of KV and current can go up to tens of KV. Moreover, the surge waveform rise time is just several μs and the lasting duration is tens of μs. Regardless of surges induced from flashover discharge between thunder clouds and flashover discharge between thunder cloud and earth or switching surge resulting from operation of power equipment, with reference to FIG. 10, the resulting energy of surge is accumulated to a sinusoidal power waveform of a power supply. This leads to the occurrence of spike distortion on the power waveform. Such waveform containing spikes puts electrical equipment having insulation design in the risk of immediate insulation degradation.
Conventional serially connected surge suppression devices have no counter design, thereby failing to learn the count of the serially connected surge suppression devices struck by surges or electromagnetic pulses. Besides, conventional serially connected surge suppression devices have no load sharing design. Once encountering special requirement having multiple surge suppression devices operated in parallel to increase load current, each parallelly connected surge suppression device easily appears to be overloading due to uneven load sharing. Such overloading phenomenon causes the parallelly connected surge suppression devices to burn down one by one, thus failing the post-stage equipment in connection to operate with normal power supply due to tripping of circuit breaker and power failure.
Furthermore, conventional serially connected surge suppression devices have no functions associated with automatic overload protection, display, automatic shunting detection recovery and the like. When the surge suppression devices are serially mounted in regular public equipment, such as road traffic signal box, builders often connect heavy construction equipment with the regular public equipment to forcibly acquire power from the public equipment. As a consequence, the serially connected surge suppression devices are overloaded and burned out. When serially applied to certain critical public equipment, such as site of telecommunication system or power supply system, the surge suppression devices can surely absorb surge and automatically disconnect from the critical public equipment once being struck by surge. However, the entire public equipment is easily shut down for sake of power failure and fails to function normally.
Also, to prevent intrusion of foreign matter, vandalism, inadvertent contact or destruction of circuits and components from affecting absorption of surge, conventional serially connected surge suppression devices are usually coated with a resin protection layer. Whereas, as surge suppression components need to withstand and absorb high-voltage current, high voltage easily accompanies with high temperature so that the surge suppression components equipped with the resin protection layer makes heat dissipation inferior and constant temperature rise of circuits degrades operational functionality and is even burned down when it goes from bad to worse.